Tuberous Tropæolum; Nat. Ord. Tropæolaceæ.
All the species of this genus are highly decorative garden subjects, including the annual varieties, and otherwise they are interesting. They are known by various names, as Trophy-plant, Indian Cress, and Nasturtium, though the latter is only applicable strictly to plants of another order. The plant under notice is a climber, herbaceous and perennial, having tuberous roots, whence its specific name; they much resemble small potatoes, and are eaten in Peru, the native country of the plant. It has not long been grown in this country, the date of its introduction being 1836; it is not often seen, which may be in part owing to the fact of its being considered tender in this climate. But let me at once state that under favourable conditions, and such as may easily be afforded in any garden, it proves hardy. As a matter of fact, I wintered it in 1880-1, and also in 1881-2, which latter does not signify much, as it proved so mild; but it must be admitted that the first-mentioned winter would be a fair test season. The position was very dry, viz., on the top of a small bank of earth, against a south wall; the soil was sandy loam, and it was overgrown with ivy, the leaves of which would doubtless keep out many degrees of cold, as also would the dryness of the soil; another point in favour of my specimen proving hardy, would be the fact of its exposure to the sun, by which the tubers would be well and duly ripened. It is one of the handsomest trailers or climbers I know for the herbaceous garden; a free grower, very floriferous, bright, distinct, and having a charming habit. The illustration (Fig. 106) can give no idea of the fine colours of its flowers, or richly glaucous foliage. One specimen in my garden has been much admired, thanks to nothing but its own habit and form; under a west wall, sheltered from the strong winds, it grows near some Lilium auratum; after outgrowing the lengths of the stems, and having set off to advantage the lily bloom, it caught by its tendril-like shoots an apricot tree on the wall, and then reached the top, being furnished with bloom its whole length. The flowers are orange and scarlet, inclining to crimson; they are produced singly on long red stalks, which spring from the axils of the leaves; the orange petals are small and overlapping, being compactly enclosed in the scarlet calyx; the spur, which is also of the same colour, is thick and long, imparting a pear-like form to the whole flower, which, however, is not more than 1½in. long. The leaves are nearly round in outline, sub-peltate, five, but sometimes only three-lobed; lobes entire, sometimes notched, smooth and glaucous; the leaf-stalks are long and bent, and act as tendrils. The plant makes rapid growth, the stems going out in all directions, some trailing on the ground.
It is a good subject for the drier parts of rockwork, where a twiggy branch should be secured, which it will soon cover. It is also fine for lattice work, or it may be grown where it can appropriate the dried stems of lupine and larkspurs. For all such situations it is not only showy, but beautiful. The flowered sprays are effective in a cut state, especially by gaslight; they come in for drooping or twining purposes, and last a long time in water.
Fig. 106. Tropæolum Tuberosum.
(One-fifth natural size.)
If grown as a tender plant its treatment is as simple as can be; the tubers may be planted in early spring in any desired situation, and when the frosts at the end of the season have cut down the foliage, the tubers may be taken up and stored in sand; but if it is intended to winter it out the situation should be chosen for its dryness, and the soil should be of a sandy nature, in which the tubers ought to be placed 5in. or 6in. deep. It is self-propagating, the tubers being numerously produced; and like "potato sets," the larger ones may be cut in pieces; if, however, numbers are not the object they are better left uncut. Caterpillars are fond of this plant; at the first sight of an eaten leaf, they should be looked for and destroyed.
It begins to flower in the latter part of summer, continuing until stopped by frosts.
Umbilicus Chrysanthus.
Nat. Ord. Crassulaceæ.